1. Field of the Invention
The present invention relates to an ink-jet head to be used for ejecting an ink for printing an image on a printing medium, an ink-jet cartridge and an ink-jet printing apparatus.
2. Description of the Related Art
An ink-jet printing system is capable of high speed and high density printing. The ink-jet printing system is also suitable for color printing and for down-sizing. Thus, such ink-jet printing system is attracting attention in the recent years.
An ink-jet printing apparatus employing such printing system has an ink-jet head 1001 and a driver mounting substrate 2001, as shown in FIGS. 10 and 11. The ink-jet head 1001 is constructed with a substrate 10, in which heating resistors (electrothermal transducer) 100 for ejecting ink droplets, a nozzle wall forming an ink passage, wiring patterns 110 and 120 (hereinafter simply referred to as "wiring") electrically connected to the heating resistors 100, an external lead electrodes 30 and so on. On the other hand, on the driver mounting substrate 2001, external lead electrodes 50 electrically connected to the external lead electrodes 30, wiring patterns 130 and 140 (hereinafter simply referred to as "wiring") and drivers IC60 for controlling the heating resistors 100 connected to the wiring 130 and 140.
The wiring formed in the ink-jet head 1001 includes individual wirings 110 and a common wiring 120. Each individual wiring 110 is formed corresponding to each heating resistor 100, one end of which is connected to one end of the corresponding heating resistor 100. The other end of each individual wiring 110 is connected to the corresponding one of external lead electrodes 30.
On the other hand, the common wiring 120 is commonly connected to the other ends of a plurality of the heating resistors 100 at one end. The other end of the common wiring 120 is connected to the corresponding external lead electrodes 30. On the other hand, a plurality of the external lead electrodes 50 of the driver mounting substrate 2001 are formed corresponding to external lead electrodes 30 of the ink-jet head 1001, respectively. To respective of those external lead electrodes 50, the individual wirings 130 and the common wirings 140 are connected.
Accordingly, each individual wiring 110 is connected to the driver IC60 for individually supplying power to the heating resistor 100 through the external lead electrodes 30 and 50 and the individual wiring 130. On the other hand, the common wiring 120 is connected to a power source via the external lead electrodes 30 and 50 and the common wiring 140. Accordingly, the common wiring 120 is commonly connected to a plurality of heating resistors 100 for permitting supply of a large current.
The individual wirings 110 and 130 are formed corresponding to the heating resistors 100. Normally, the individual wirings 110 and 130 are formed in the same interval as that of the heating resistors 100. Namely, the individual wirings 110 and 130 are formed in the interval of 200 DPI to 1200 DPI corresponding to nozzles. Under the premise of such interval, the layer thickness of the individual wirings 110 and 130 are determined for achieving easiness of manufacturing of the ink-jet head, electrical property and reliability of the heating resistor portion. Property required for the individual wirings 110 and 130 is as follow.
A. Reduction of Wiring Resistance PA0 B. In order to improve coverage of a protection layer in the vicinity of the heating resistor 100, it is necessary to make the layer thickness of the individual wirings 110 as thin as possible. PA0 C. The ink-jet head 1001 or the driver mounting substrate 2001 are formed by photolithographic method for achieving high density of wiring. In order to form high density wiring, the layer thickness of the wiring has to be as thin as possible. PA0 A'. Since power is supplied to a plurality of heating resistors 100, it is necessary to make cross-sectional area of the common wiring 120 and 140 as wide as possible in order to improve efficiency. Namely, it is necessary to make the layer thickness as thick as possible or to make the area as wide as possible. PA0 A". In order to certainly maintain reliability of electrical connection between the ink-jet head 1001 and the driver mounting substrate 2001, it is essential to consider mutual tolerance in assembling. Therefore, it is necessary to make the interval between the electrodes 30 and 50 as wide as possible. PA0 1. Since the fabrication processes of the individual wirings 110 and 130 and the common wiring 120 and 140 are different, fabrication process for fabricating the ink-jet head 1001 and the driver mounting substrate 2001 becomes complicate. PA0 2. Since the individual wirings 110 and 130 and the common wiring 120 and 140 have to be formed in multi-layer wiring, an interlayer insulation layer having quite high reliability is required, and caused to lower yield in the fabrication process. PA0 3. Shapes of the external lead electrodes 30 and 50 formed by plating or the like are bump shaped configuration, and the shapes of the common wiring 120 and 140 are line shape and have wide pattern area. Therefore, it is difficult to form the external lead electrodes 30 and 50 with a uniform height.
In order to increase proportion of the power to be effectively supplied to the heating resistor 100 among a power supplied to the heating resistor 100, it is necessary to reduce resistance of the individual wirings 110 and 130 as much as possible.
On the other hand, properties required for the common wiring 120 and 140 are as follows:
Also, the external lead electrodes 30 and 50 are required the following requirement.
For the above requirement, the individual wirings 110 and 130 are formed by thin film processing as photolithographic method, and the common wiring 120 and 140 are formed by plating or thick film processing. Also, the individual wirings 110 and the common wiring 120 are formed in multi-layer wiring.
However, the following problems are encountered in the conventional fabrication processes of the individual wirings 110 and 130 and the common wiring 120 and 140.